1. Field of the Invention
The present invention relates to a reception device and a reception method for receiving signals and a transmission reception system including a transmission device and a reception device.
2. Description of the Related Art
In visible light communication as wireless communication, signal light is emitted from an LED (Light-Emitting Diode) of a transmission unit of a transmission device and the signal light is received by a light receiving sensor (PD: photodiode) of a reception unit of a reception device. The transmission device includes an analog circuit for driving the LED, while the reception device includes an analog circuit for amplifying an output from the PD. When a signal is transmitted by using a PSK (Phase Shift Keying) modulation method, the signal waveform after the modulation has high-frequency components at symbol boundaries in many cases. The signal after the modulation passes through the analog circuit for driving the LED and also passes through the analog circuit for amplifying the output from the PD. In a case where the signal waveform input to an analog circuit has high-frequency components, distortion can occur in the signal waveform and the influence of the distortion increases with an increase in the high-frequency components.
In a case of low-speed communication for transmitting a small amount of data such as position information, the distortion due to the high-frequency components at the symbol boundaries is low enough to have no influence on the demodulation performance since the symbol length in PSK is long. However, in a case of high-speed communication for transmitting a large amount of data such as images and videos, the symbol length is short, and thus there is the possibility of an increase in the distortion due to the high-frequency components at the symbol boundaries and deterioration in reception quality such as the demodulation performance.
Patent Document 1 discloses a reception device including a computation unit that makes compensation for distortion occurring in an analog circuit.
Patent Document 1 is Japanese Patent Application Publication No. 2011-250007.
However, the reception device described in Patent Document 1 performs nonlinear computation having a great amount of calculations as the computation for making the compensation for the distortion occurring in the transmission device, and thus has a problem in that a computation unit having high processing power is necessary.